Computer hard drives typically employ a number of rapidly rotating disks having a coating of magnetic data storage material. Each disk is matched with a magnetic read/write head that is held very close to the disk surface. The magnetic read/write head can read and write data on the magnetic disk as it moves.
Some hard drives have disks with nonstick portions that will not cause damage to the magnetic heads if the heads rest on the nonstick portion for an extended period of time. Such hard drives are known as contact start/stop (CSS) hard drives. A CSS hard drive does not require a lift tab or load/unload ramp.
The magnetic head is prevented from contacting the disk surface by a cushion of air moving with the disk. Typically, the magnetic head is about 0.02 microns away from the disk while the disk is moving.
The need for very small spacing between the head and disk during the operation of the drive requires that the head and disk surfaces be very smooth. In non-CSS hard drives it is important for the magnetic head and disk surface not to come in contact when the disks are not rotating (i.e., when the hard drive is not powered). If a disk and magnetic head are at rest and in contact for a period of time, the head and disk surface can stick together, resulting in damage to the disk surface when the disks start to rotate. In some cases the stiction force can prevent the disks from rotating altogether. Also, the disk must start from rest, and a certain minimum velocity is required for the magnetic head to float over the disk surface. Therefore, each startup of the hard drive can result in the magnetic head and disk surface rubbing for a distance until the disk achieves sufficient speed to form the air cushion.
For these reasons, load/unload ramp structures have been used in some hard drives to hold the magnetic heads away from the disk surfaces while the hard drive is not operating. The magnetic heads are released from the ramp structure when the disks have achieved the minimum speed for causing the magnetic heads to float above the disk surfaces. CSS hard drives do not have load/unload ramp structures or lift tabs.
FIG. 1 (prior art) shows a typical prior art load/unload type hard drive with three disks 2. An actuator arm 3 supports a suspension 4, a slider 5 and a lift tab 6. A magnetic read/write head (not shown) is located on a bottom surface of the slider 5. The suspension 4 and slider 5 together comprise a head gimbal assembly. The actuator arm 3 pivots about a pivot post 9. The lift tab 6 is positioned on the suspension 4 so that it engages a ramp 8 on a ramp structure 10. The ramp 8 imparts an upward force on the lift tab 6 which lifts the slider 5 and magnetic head away from the disk 2. The magnetic head is thereby not in contact with the disk 2 whenever the lift tab 6 is moved onto the ramp 8. In order for the lift tab 6 to lift the slider from the disk, the lift tab 6 must rub against the ramp 8.
Although not shown in FIG. 1, the hard drive has additional arms, suspensions and sliders so that there is at least one suspension and slider for each disk surface.
FIG. 2 (prior art) shows a closeup side view of a lift tab 6 engaging the ramp 8. Shown are three different positions for the lift tab 6. A rounded bottom surface 12 of the lift tab 6 must rub against the ramp 8 in order for the slider to be lifted from the disk 2. The slider 5 is unloaded from the disk as the lift tab moves from left to right, and loaded onto the disk 2 as the lift tab moves from right to left.
Typically, the ramp structure 10 is made from low-friction polymer materials. Low friction ramps 8 reduce the amount of energy required to unload the magnetic heads (a concern during unpowered unloading).
Lift tabs are typically made of metal such as stainless steel. Since they are harder than the ramp structure (made of plastic), the lift tab may abrade the ramp during loading and unloading. Abrasion creates contaminate particles within the hard drive that can damage the sensitive slider/disk interface. It is therefore necessary for the bottom lift tab surface (which contacts the ramp) to be as smooth as possible. A smooth lift tab surface produces fewer particles when rubbed over the surface of the ramp.
Of particular concern are lift tabs stamped from sheet metal. This is because the process for making sheet metal, and the stamping process, produce relatively rough surfaces.
One method used in certain IBM products to smooth the lift tab is to press the lift tab against a very smooth and hard die. This `coining` process smoothes the surface by closing cracks in the lift tab surface and planarizing protrusions. Smoothness is limited by the surface quality of the die and the pressure used. Lift tabs smoothed by the coining process still produce rather large numbers of particles when rubbed against a ramp.
There exists a need in the art for improved methods of smoothing the lift tab. Such a method would provide for reduced particulate contamination inside a data storage hard drive, leading to higher reliability.